LONDON, England (CNN) -- The British man who reappeared five years after he was thought to have drowned changed his identity during his disappearance and tried to buy a catamaran to go "sailing around the world," a boat dealer said Friday.

It comes as a judge in Hartlepool Magistrates' Court in northeast England granted police another 36 hours to question John Darwin, 57. Police had sought a warrant for an extension of his detention.

Robert Hopkin, of Gibraltar, said Darwin came to see him in November 2005 over the sale of a 60-foot catamaran worth £45,000 ($91,000). Gibraltar is a British territory on the southern tip of Spain.

Hopkin said Darwin introduced himself as John Jones and that he acted "a little bit suspicious."

Darwin walked into a police station in London last week, and claimed to have amnesia. He was arrested late Tuesday on suspicion of fraud. His wife, Anne, is believed to be in the United States after leaving Panama on a flight late Thursday, a Panamanian immigration representative told CNN.

She collected his life insurance money in 2003, after he was officially declared dead. The remains of a kayak he paddled into the North Sea off the coast of Seaton Carew had washed up on shore the year before.

Hopkin, the boat dealer, described his meeting with Darwin to CNN.

"He said the boat was for him and his partner and he was going sailing around the world," Hopkin said. "He seemed suspicious of me. He seemed suspicious of everyone."

Hopkin said the sale fell through after Darwin walked away from the deal.

The catamaran owner said he only realized Darwin was the same man who had come to visit him when he received a call from police in Britain investigating the missing man, who had traced paperwork to his business.

On Thursday, the couple's sons said they feared they may have been the victims of a "huge scam" carried out by their own parents.

In a joint statement released by police, Darwin's sons, Mark, 31, and Anthony, 29, said they were in an "angry and confused state of mind" and they wanted no further contact with their parents.

A Cleveland Police spokeswoman said Friday they wanted to speak to Anne Darwin.

"We are aware of media speculation regarding Mrs. Darwin. At this stage we do not know of her whereabouts. However we can confirm that if and when Mrs. Darwin does appear in Britain then police want to speak to her as a matter of urgency," the spokeswoman said.

Following media reports Thursday that Anne Darwin had confessed to knowing her husband was alive, the sons said: "If the papers' allegations of a confession from our mam are true, then we very much feel that we have been the victims in a large scam."

Anne Darwin was tracked down by reporters to her new Central American home in Panama City where she moved six weeks ago.

The British tabloid newspaper the Daily Mirror reported that the wife broke down crying when she was shown a photograph, which appeared to show her posing with her husband in the Panamanian capital last year.

Reacting to the photo, Anne Darwin, who had earlier said in a statement released through her sons that she had not seen her husband in the last five years, said "my sons are never going to forgive me," the paper reported.

"In the short space of time following our dad's appearance in London on Saturday, we have gone through a rollercoaster of emotion," said the sons' statement, released through Cleveland Police, the force investigating the case. E-mail to a friend